With discoveries of the past (e.g., Mariner, Pioneers, Ulysses) and the present (e.g., Voyager, SOHO/SWAN, IBEX, New Horizons) heliospheric missions, the exploration of the heliosphere, its boundary regions, the outer reaches of our solar system, as well as the Very Local Interstellar Medium (VLISM) has profoundly changed the view of our space in the universe. The Interstellar Mapping and Acceleration Probe (IMAP) is a future space mission dedicated to study the interaction of the solar wind with the interstellar medium and the acceleration of energetic particles. These two topics are crucial for understanding the coupling between the inner and the outer heliosphere. The Interstellar Probe escaping beyond the solar-system boundaries with new measurements would be crucial to enable the new understanding and discoveries of the global heliosphere, the interstellar medium, the Kuiper Belt, the circumsolar dust disk, and the evolution of our solar system. This session focuses on advancing the understanding of the heliosphere and its interaction with VLISM as well as the groundbreaking science of interstellar exploration, instrumentation for relevant in-situ and remote measurements, and the relevant mission and spacecraft concepts.

Convener: Justyna M. SokolECSECS | Co-conveners: André Galli, Olga KatushkinaECSECS, Linghua Wang, George Ho, Robert F. Wimmer-Schweingruber
| Attendance Wed, 06 May, 08:30–10:15 (CEST)

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Chat time: Wednesday, 6 May 2020, 08:30–10:15

Chairperson: André Galli
D2817 |
| Highlight
Qiugang Zong

Supersonic solar wind streams away from the Sun in all directions, interaction with the local interstellar medium to form a giant plasma bubble, which is coined by A. J. Dessler as “heliosphere”. Voyager 1& 2 spacecraft have recently encountered the heliospheric boundaries of this plasma bubble, e.g. the termination shock, heliosheath and heliopause.

To explore further on the dynamics on the heliospheric boundaries, even the hydrogen wall, and the local interstellar medium,  an Interstellar Heliosphere Probes (IHPs)mission have been proposed to Chinese national space agency (two spacecraft, one towards the nose of the heliopause, one opposite). The plan is that the spacecraft is to reach 100AU when it is 100th anniversary of the PR China (2049). Thus, IHP will allow us to discover, explore, and understand fundamental astrophysical processes in the largest plasma laboratory-- the heliosphere.

How to cite: Zong, Q.: Interstellar Heliosphere Probes (IHPs), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3981, https://doi.org/10.5194/egusphere-egu2020-3981, 2020.

D2818 |
| Highlight
Ralph McNutt, Mike Gruntman, Stamatios Krimigis, Edmond Roelof, Pontus Brandt, Kathleen Mandt, Steven Vernon, Michael Paul, and Robert Stough

An “Interstellar Probe” to the nearby interstellar medium has been discussed in the scientific community for almost 60 years. The key concept has always been to depart from the Sun outward “as fast as possible.” Scientific goals have principally focused on heliospheric topics throughout multiple studies, with potential “bonus science” in both astrophysics and planetary science. The passages of Voyagers 1 and 2 into that medium have only raised multiple new questions, rather than “solving” the outstanding question of the interaction of the solar wind with the nearby interstellar medium. In particular, solar activity apparently continues to have an effect on nearby interstellar space, magnetic field changes in crossing from the heliosheath into the local medium are only in magnitude and not direction, and the three-dimensional structure of the energetic neutral atom (ENA) “ribbon” remains unknown. The power levels on the Voyagers continue to decrease toward the operational floor which is likely to be reached within the next five years, limiting the extent of our exploration, and ending heliophysics deep-space measurements beyond the asteroid belt for the indefinite future. The salient question for a dedicated mission is “What can the Interstellar Probe do that no other mission can do?” The answer requires an in-depth look at current capabilities for such a mission, e.g., solar system escape speed, data downlink bandwidth, and mission lifetime with science topics, technological readiness of mission and instrument concepts, and realistic mission costs. To provide technical input to the upcoming Solar and Space Physics Decadal Survey, NASA has contracted with the Johns Hopkins University Applied Physics Laboratory (APL) to execute a “First Pragmatic Interstellar Probe Mission Study.” The effort focuses on near-term engineering readiness (ready for launch by 2030) but also includes input regarding compelling science and associated required measurements and instrumentation, assuming that such a mission would commence during the next Decadal time period. This is not a Science Definition Team (SDT) exercise, but rather an assessment of possibilities. In that spirit, we continue to seek input from across the international space science community regarding potential science goals, measurements, instruments, and their implementation readiness in order to help inform the engineering team in support of a concept mission. We provide a status report on this ongoing effort.

How to cite: McNutt, R., Gruntman, M., Krimigis, S., Roelof, E., Brandt, P., Mandt, K., Vernon, S., Paul, M., and Stough, R.: Interstellar Probe: The Next Step, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6119, https://doi.org/10.5194/egusphere-egu2020-6119, 2020.

D2819 |
| Highlight
Jeffrey Linsky

 We describe the very local interstellar medium (VLISM)
immediately outside of the outer heliosphere. The VLISM consists 
of four partially ionized clouds - the Local Interstellar Cloud (LIC), 
G cloud, Blue cloud, and Aql cloud that are in contact with the outer 
heliosphere, and ionized gas produced by extreme-UV radiation 
primarily from the star Epsilon CMa. We construct the 
three-dimensional shape of the LIC based on interstellar line 
absorption along 62 sightlines and show that in the direction of 
Epsilon CMa, Beta CMa, and Sirius B the neutral hydrogen column 
density from the center of the LIC looking outward is a minimum. 
We call this region the ``hydrogen hole''. In this direction, the 
presence of Blue cloud absorption and the absence of LIC absorption 
can be simply explained by the Blue cloud lying just outside of the 
heliosphere. We propose that the outer edge of the Blue cloud is a 
Str\"omgren shell driven toward the heliosphere by high pressures in 
the H II region. The outer edges of other clouds facing Epsilon CMa 
are likely also Stromgren shells. Unlike previous models, the LIC
surrounds less than half of the heliosphere.

We find that the vectors of neutral and ionized helium flowing
through the heliosphere are inconsistent with the mean LIC flow 
vector and describe several possible explanations. The ionization
of nearby intercloud gas is consistent with photo-ionization by 
Epsilon CMa and hot white dwarfs without requiring additional 
sources of ionization or million degree plasma. In the upwind 
direction, the heliosphere is passing through an environment of 
several LISM clouds, which may explain the recent influx of 
interstellar grains containing 60Fe from supernova ejecta measured 
in Antarctica snow. The Sun will leave the outer partof the LIC 
in less than 1900 years, perhaps this year, to either enter the 
partially ionized G cloud or a highly ionized intercloud layer. 
The heliosphere will change in either scenario. An instrumented 
deep space probe sending back in situ plasma and magnetic field 
measurements from 500-1,000 AU is needed to understand the 
heliosphere environment rather than integrated data along the 
sightlines to stars.  

How to cite: Linsky, J.: What lies immediately outside of the heliosphere in the very local interstellar medium (VLISM): morphology of the Local Interstellar Cloud, its hydrogen hole, Stromgren Shells, and 60Fe accretion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1410, https://doi.org/10.5194/egusphere-egu2020-1410, 2020.

D2820 |
| Highlight
David McComas

This talk provides an overview of the Interstellar Mapping and Acceleration Probe (IMAP) mission and what we hope and expect to learn from it. IMAP is currently in Phase B and is slated to launch in the fall of 2024. IMAP simultaneously investigates two of the most important, and intimately coupled, research areas in Heliophysics today: 1) the acceleration of energetic particles and 2) the interaction of the solar wind with the local interstellar medium. IMAP’s ten instruments provide a complete set of observations to simultaneously examine the particle injection and acceleration processes at 1 AU while remotely dissecting the global heliospheric interaction and its response to particle populations generated through these processes. For more information about IMAP, see: McComas, D.J., et al., Interstellar mapping and acceleration Probe (IMAP): A New NASA Mission, Space Science Review, 214:116, doi:10.1007/s11214-018-0550-1, 2018.

Open Access: https://link.springer.com/article/10.1007%2Fs11214-018-0550-1 

How to cite: McComas, D.: Overview of the Instellar Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5547, https://doi.org/10.5194/egusphere-egu2020-5547, 2020.

D2821 |
Igor Baliukin, Vladislav Izmodenov, and Dmitry Alexashov

The Interstellar Boundary Explorer (IBEX) spacecraft has been measuring fluxes of the Energetic Neutral Atoms (ENAs) using the IBEX-Hi (0.3 – 6 keV) instrument since 2008. We have developed the numerical model to calculate ENA hydrogen fluxes employing reconstruction of the trajectories of the atoms (backward in time) from 1 au, where they are observed by IBEX, to the point of their origin in the inner heliosheath, i.e. the region of the perturbed solar wind between the termination shock and the heliopause, where the plasma is strongly heated (T ~ 106 K). Along the trajectory of the atom, differential fluxes of the newly originated ENAs with a given speed are integrated, and losses due to ionization processes (charge exchange with protons and photoionization) are also taken into account.

The key factor in the simulation is a detailed consideration of the supra-thermal component of pickup ions (PUIs) that originate in the region of the supersonic solar wind and picked by the heliospheric magnetic field since this component is «parental» to the ENA. We take into account the supra-thermal component by solving the kinetic equation under the assumption that PUI distribution function is isotropic everywhere in the heliosphere. This method compares favorably with other existing approaches since it is based on fundamental physical laws.

We have calculated model maps of the ENA fluxes based on the previously developed kinetic-MHD models of the SW/LISM interaction (Izmodenov & Alexashov, 2015, 2020), and performed the comparison with IBEX-Hi data. The IBEX-Hi data is one of the few sources of knowledge about the structure of the heliospheric boundary, imposing significant limitations on the parameters of the model of the heliosphere. As a result of the comparison, we concluded that 1) ENA fluxes from the region of the inner heliosheath are extremely sensitive to the form of PUI distribution function; 2) the model of the heliosphere Izmodenov & Alexashov (2020) that differs from the model Izmodenov & Alexashov (2015) in configuration of the interstellar magnetic field reproduces the IBEX-Hi data better; 3) despite a relatively good agreement, there are some qualitative differences between the model calculations and IBEX-Hi data in some energy channels of IBEX-Hi. The reasons for these differences are discussed.

How to cite: Baliukin, I., Izmodenov, V., and Alexashov, D.: Heliospheric Energetic Neutral Atoms: Numerical Modelling and Comparison with IBEX-Hi data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18777, https://doi.org/10.5194/egusphere-egu2020-18777, 2020.

D2822 |
Pawel Swaczyna, David J. McComas, Eric J. Zirnstein, and Jacob Heerikhuisen

Interstellar neutral (ISN) atoms from the very local interstellar medium (VLISM) penetrate the heliosphere and are observed by detectors located near 1 au, e.g., on the Interstellar Boundary Explorer (IBEX), and in the future on the Interstellar Mapping and Acceleration Probe (IMAP). Interpretation of these observations provides insight into the physical conditions in the VLISM but requires modeling of the processes that change distributions of ISN atoms inside the heliosphere and beyond. Here, we focus on the consequences of collisional scattering in the outer heliosheath (OHS), beyond the heliopause. Charge exchange collisions create secondary atoms from the OHS ions, which have a different flow speed and temperature than pristine ISN atoms, especially close to the heliopause. It is widely assumed that these collisions do not change directions of interacting particle velocities. We show that this assumption is not justified for the typical collisions speed in the OHS, and therefore the distribution functions of secondary atoms are different than those calculated without this momentum exchange.  This angular scattering in charge exchange collisions results in secondary atom production terms that show elongated distributions aligned with the relative bulk speed of the parent populations, as well as higher temperatures (up to ~3000 K) and shifted bulk speeds (up to ~2 km s-1). Distributions of ISN atoms are also affected by elastic collisions that similarly show significant scattering for collision energies typical in the OHS. Eventually, these scattering processes modify distributions of ISN atom observed in the heliosphere directly and as pickup ions. These effects may help explain systematical discrepancies between the IBEX data and current models.

How to cite: Swaczyna, P., McComas, D. J., Zirnstein, E. J., and Heerikhuisen, J.: Scattering of Interstellar Neutral Atoms in the Outer Heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10815, https://doi.org/10.5194/egusphere-egu2020-10815, 2020.

D2823 |
Amenehsadat Mousavianzehaie, Kaijun Liu, and Kyungguk Min

Kinetic linear instability analysis and hybrid simulations are carried out to examine the role of mirror instability in scattering the pickup ions in the outer heliosheath. The dynamics of these pickup ions is essential to
the understanding of the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer
(IBEX). While most previous studies have focused on the ion cyclotron instability driven by the pickup ions,
recent work based on a simple ring velocity distribution of the pickup ions suggested that the mirror mode can
also be unstable and contribute to the scattering of the pickup ions. The present study performs linear analysis
as well as hybrid simulations for a more realistic, multi-component pickup ion velocity distribution given by the
global modeling of neutral atoms in the heliosphere. The linear theory results indicate unstable mirror modes
with considerable growth rates. The corresponding hybrid simulations further confirm that the mirror modes can
grow and aid the pitch-angle broadening of the pickup ions. So the role of mirror mode should not be ignored in
the stability study of the outer heliosheath pickup ions.

How to cite: Mousavianzehaie, A., Liu, K., and Min, K.: Mirror instability driven by pickup ions in the outer heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2107, https://doi.org/10.5194/egusphere-egu2020-2107, 2020.

D2824 |
Maciej Bzowski, Marzena Kubiak, and Jacob Heerikhuisen

Interaction between the solar wind and the local interstellar environment has been studied using several observation techniques, including in-situ sampling of the plasma, magnetic field,  energetic ions by the Voyager spacecraft; remote-sensing observations of energetic neutral atoms (IBEX, Cassini); and the primary and secondary populations of interstellar neutral gas (IBEX-Lo). Understanding the processes at the heliospheric boundary and of the conditions outside the heliosphere is typically  done by fitting parameters used in models of this interaction to various observables, including the Voyager crossing distances of the termination shock and the heliopause, the size of the IBEX ribbon and its center directions, the sky distribution of the Lyman-alpha helioglow, and the flux of interstellar gas at 1 au from direct-sampling observations. Typically, it is expected that all or most of these observables are successfully reproduced. Even though the interaction of interstellar neutral gas with the solar wind and solar EUV output is sometimes taken into account, the global heliosphere is usually simulated as a stationary structure, with the solar wind flux, density, and magnetic field variation ignored. However, solar wind is a dynamic phenomenon, which results in variations in the plasma flow both inside and outside the heliopause and in variations of the distance to the heliopause. Based on in-situ solar wind observations, dynamic pressure of the solar wind may change by a factor of 2, which may result in a heliopause distance change by 50%, counting from the lowest-pressure conditions.

Interstellar neutral atoms reaching detectors at 1 au or contributing to the helioglow observed from 1 au need very different times to travel from the interaction  region , typically located at ~1.75 of the heliopause distance to 1 au. While the primary ISN atoms take 3—4 solar cycles to travel from this region to 1 au, with a physical time spread (not an uncertainty!) of about one solar cycle, the atoms from secondary population take as much as 15 solar cycles, with a large spread of 7 solar cycles. This implies that ISN He atoms sampled by IBEX-Lo, as well as those observed as the helioglow, originate from two different and disparate epochs. While it may be expected that the interstellar conditions at a time scale of 200 years are little variable, solar wind is definitely varying, with secular changes superimposed on the solar cycle variation.

Direct-sampling observations provide information on the plasma flow in the OHS inside ~60° around the inflow direction, with well-defined regions of the OHS contributing atoms to individual pixels observed by IBEX and IMAP at different orbits. However, the information obtained is heavily averaged over time, and the epoch  imprinted on these population is very different to the epochs characteristic for in-situ observations from the Voyagers (by 50 to 170 years!)  and remote-sensing observations of the much faster-running energetic neutral atoms.

How to cite: Bzowski, M., Kubiak, M., and Heerikhuisen, J.: What epoch and space region at the heliospheric boundaries are probing IBEX and IMAP observations of interstellar neutral gas populations?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9610, https://doi.org/10.5194/egusphere-egu2020-9610, 2020.

D2825 |
Hans-Jörg Fahr

In this presentation solar wind electrons and protons are studied which, after their passage over the solar wind termination shock, are convected downstream into the heliosheath. Due to the electric nature of this shock, downstream electrons appear highly energized with non-equilibrium,  kappa-like  distributions . When looking upon the moments of these downstream electrons and protons, it turns out as a surprise that the pressure of the electrons, compared to the protons, is larger by a factor of 2. Then it is taken into account that the pressure of kappa-distributed particles contains contributions from particles with super-luminal velocities which need to be removed from the pressure values . Even when these reductions are carried out, it is manifest that the heliosheath pressures of electrons and protons are of equal orders of magnitudes. In conclusion it is found that there is no pressure deficit in the heliosheath with respect to the ambient interstellar medium.

How to cite: Fahr, H.-J.: The pressure-relevance of suprathermal solar wind electrons for the heliosheath, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-63, https://doi.org/10.5194/egusphere-egu2020-63, 2020.

D2826 |
Roman Gomez, Stephen Fuselier, James Burch, Joey Mukherjee, Carrie Gonzalez, Karlheinz Trattner, Michael Starkey, and Robert Strangeway

The Sun and its associated heliosphere travels through the local interstellar medium (LISM) at 26 km/s.  This results in a flow of neutral particles constantly entering the heliosphere at the same velocity.  Neutral atoms with trajectories close to the Sun, which survive its ionizing radiation environment, become gravitationally attracted to it resulting in a focusing cone, a region of enhanced neutral density, downwind of the Sun.  The increased neutral density in these regions leads to a higher density of pickup ions created by charge-exchange of the neutrals.  In near-Earth orbit, the Magnetospheric Multiscale spacecraft (4 in all) have orbital apogees on the dayside during Earth’s annual encounter with the helium focusing cone (from mid-November to mid-December).  Since launching in March of 2015, regular acquisitions with the Hot Plasma Composition Analyzers (HPCAs) have been conducted, with acquisitions from 2017 through 2019 occurring with a 29 RE apogee, ensuring long intervals in the pristine Solar Wind.   We provide measurements of the focusing cone during the declining phase of the previous solar cycle. These measurements are used to investigate the effect of solar radiation on the focusing cone.

How to cite: Gomez, R., Fuselier, S., Burch, J., Mukherjee, J., Gonzalez, C., Trattner, K., Starkey, M., and Strangeway, R.: Temporal measurements of the interstellar helium focusing cone by the Magnetospheric Multiscale Mission(MMS), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2187, https://doi.org/10.5194/egusphere-egu2020-2187, 2020.

D2827 |
Olga Katushkina, Vladislav Izmodenov, and André Galli

This work is devoted to the analysis of the interstellar hydrogen fluxes measured by IBEX spacecraft from 2009 to 2018. To calculate the fluxes we use our 3D time-dependent kinetic model of the hydrogen distribution in the heliosphere that takes into account non-maxwellian behavior of the velocity distribution function of hydrogen atoms due to charge exchange with protons at the heliospheric boundary. The temporal variations of the hydrogen fluxes during the entire solar cycle are considered and analyzed by comparison of the IBEX-Lo data and the model results. During solar maximum the measured fluxes are too low, therefore we choose several years 2009-2011 and 2017-2018 when the signal-to-noise ratio is appropriate. A parametric search is performed to determine the influence of different model parameters on the full sky maps of the fluxes. It is found that solar radiation pressure is the most crucial parameter for the position of the maximum fluxes, while the heliolatitudinal variations of the charge exchange ionization rate influence the shape of the maps during solar minimum conditions. The quantitative differences between the data and the model results are demonstrated, and several possible reasons for them are discussed.

How to cite: Katushkina, O., Izmodenov, V., and Galli, A.: Low energetic Interstellar hydrogen atoms in the heliosphere: Decade of IBEX observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18647, https://doi.org/10.5194/egusphere-egu2020-18647, 2020.

D2828 |
Justyna M. Sokol

Solar wind and EUV flux are dominant ionization factors for the interstellar gas inside the heliosphere. They vary in time with the solar cycle and with heliographic latitude. The modulation of the solar ionizing factors affects the fluxes of interstellar neutral (ISN) gas and energetic neutral atoms (ENAs) on their way from heliospheric boundaries to IBEX in the Earth’s vicinity. IBEX has been measuring ISN gas of hydrogen, helium, neon, and oxygen, as well as hydrogen ENAs since the beginning of the solar cycle 24. Most of the ISN gas species observed by IBEX-Lo are prone to variations in time of the in-ecliptic ionization rates. In case of H ENAs, variations of the out-of-ecliptic solar wind are significant for data interpretation.

We present a model of ionization rates based on available observations of the solar wind and the solar EUV flux. We follow methodology discussed by Sokół et al. 2019 (ApJ 872:57), however with data selection revised according to recent data releases. We focus on ionization rates for various species in and out of the ecliptic during the decade of IBEX observations. We discuss similarities and differences in the dominant ionization processes, the latitudinal modulation, and the evolution in time.

How to cite: Sokol, J. M.: Observation-based Ionization Rates during the Decade of IBEX Observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6167, https://doi.org/10.5194/egusphere-egu2020-6167, 2020.

D2829 |
Jonathan Gasser, Peter Wurz, and André Galli

The Interstellar Mapping and Acceleration Probe (IMAP) mission by NASA, to be launched in 2024, aims at deepening the understanding of the solar heliosphere by verifying and extending the results obtained from the Interstellar Boundary Explorer (IBEX). IMAP-Lo is a neutral atom imaging and analysis instrument to be used to measure heliospheric Energetic Neutral Atoms (ENAs), mainly H, He, O, Ne in the energy range from 10 eV to 1 keV. One key point of improvement of IMAP-Lo compared to IBEX-Lo is having more accurate calibration methods for ENAs at hand. The IMAP-Lo calibration will be carried out in MEFISTO, a calibration facility for ion and neutral particle instruments at the University of Bern. MEFISTO consists of an ion beam source with energies 10 eV/q - 100 keV/q, a removeable beam neutralization stage for neutral atoms from 10 eV to 3 keV, and a large vacuum test chamber.

The beam neutralization process relies on a charge conversion surface and thus results in an energy loss of about 15%, and energy-dependent transmission. It is therefore essential to be able to measure the effective neutral particle flux and beam energies provided at the exit of the neutraliser to improve the calibration process for an ENA instrument, such as IMAP-Lo.

The Absolute Beam Monitor (ABM) is a new laboratory device dedicated to measure the absolute neutral particle flux and coarse energy distribution of a neutral atom beam. The present prototype consists of a tungsten start surface [GJ(1] and two electron multipliers contained in a box of about 1 dm3 volume. By counting the start, stop and coincidence signal rates we infer the effective number of neutral atoms. In addition, the particle energy is determined by a time-of flight measurement.

We present the measurement principle and demonstrate the validity of the concept with the ABM prototype. Neutral H, He, and O beams at different energies and fluxes have been evaluated in MEFISTO with the ABM prototype. The results are compared with IBEX-Lo calibration measurements.

How to cite: Gasser, J., Wurz, P., and Galli, A.: Absolute Beam Monitor: a device to measure the absolute particle flux of a neutral atom beam – prototype development and testing, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3302, https://doi.org/10.5194/egusphere-egu2020-3302, 2020.

D2830 |
Pontus Brandt, Kathleen Mandt, Elena Provoronikova, Casey Lisse, Kirby Runyon, Abigail Rymer, Ralph McNutt, and Michael Paul and the The Interstellar Probe Study Team

An Interstellar Probe beyond our heliosphere in to the largely unexplored interstellar medium (ISM) would be the furthest and boldest step in robotic space exploration ever taken. A dedicated payload of in-situ and remote sensing instruments would uncover the new regime of physics at work in the heliospheric boundary region and offer the first external view of the global heliosphere that is currently missing in the family portrait of all other types of astrospheres observed. Beyond about 400 AU the Probe would reach the ISM and for the first time begin its sampling of the properties of the local interstellar cloud (LIC) that our Sun and neighboring star systems are immersed in.

An Interstellar Probe has been discussed since around 1960 in several NASA and international studies. The compelling science objectives have remained almost unchanged and are focused on understanding the plasma physics in the interaction region between the heliosphere and the ISM. Their importance have been amplified by the recent unexpected findings by the Voyager 1 and 2 spacecraft that are nearing their end of life at less than 150 AU from the Sun. Remote observations in Energetic Neutral Atoms (ENAs) by the NASA IBEX and Cassini missions have made the remarkable discoveries of ENA emission morphologies that have come as a complete surprise and still lack a satisfactory explanation. Hubble Space Telescope observations have now also made it clearer that the Sun is about to exit the LIC and perhaps already has, which is a unique event of astronomical scales that an Interstellar Probe could explore in-situ for the first time. In addition to these top-priority objectives, contributions of unprecedented science value to planetary sciences and astrophysics are possible including flybys of at least one Kuiper Belt Object, in-situ and remote observations of the dust debris disk, and the extra-galactic background light.

Here we review the outstanding questions and current state of understanding of the global heliosphere, the ISM and what planetary and astrophysics augmentations can offer. We summarize the compelling science case for an Interstellar Probe, including a range of possible science payloads and the associated operation scenarios. The results stem from the study of a Pragmatic Interstellar Probe currently underway, funded by NASA, and led by The Johns Hopkins University Applied Physics Laboratory with active participation from a large, international team of scientists and engineers. The study focuses on finding realistic mission architectures among a trade space of propulsion options, trajectories, risks and reliability challenges. The study considers operation out to 1000 AU, a survival probability of 85% over 50 years and electrical power of no less than 400 W at the beginning of mission. Over twice the speed of Voyager 1 (the fastest spacecraft currently) has already been achieved in the design using conventional propulsion, with a direct inject to Jupiter followed by a Jupiter Gravity Assist. In order to provide input requirements to the mission study, several possible payloads with different mass allocations and associated mission requirements, trade-offs and risks have been identified.

How to cite: Brandt, P., Mandt, K., Provoronikova, E., Lisse, C., Runyon, K., Rymer, A., McNutt, R., and Paul, M. and the The Interstellar Probe Study Team: Interstellar Probe: Pushing the Frontier of Space Science, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19605, https://doi.org/10.5194/egusphere-egu2020-19605, 2020.

D2831 |
| Highlight
Bernd Heber, Robert Wimmer-Schweingruber, Marlon Köberle, Patrick Kühl, and Stephan Böttcher

The recent AMS 02 measurements show that the very local interstellar spectra (VLIS) for galactic cosmic rays cannot be directly measured at the Earth below rigidities of 40-60 GV because of solar modulation. With Voyager 1and Voyager II crossing the heliopause in 2012 and 2018, in situ experimental LIS data below 100 MeV/nuc constrain computed galactic CR spectra. However, the energy spectra in between can so far only be derived by models. This gap could be narrowed by flying an instrument like the The COsmic and Solar Particle INvestigation Kiel Electron Telescope (COSPIN/KET) that measured protons and alpha-particles in the energy range from about 4 to above 2000 MeV/n and electrons in the range up to 10 GeV in distinguished energy channels. Such a telescope would consist of two parts: 1) an entrance telescope of two semiconductors comprising a silica-aerogel Cherenkov detector with a refractive index of 1.066, selecting particles with speeds v/c = b > 0.938, and 2) a calorimeter, a lead-fluoride Cherenkov detector followed by a scintillation detector measuring escaping particles.

How to cite: Heber, B., Wimmer-Schweingruber, R., Köberle, M., Kühl, P., and Böttcher, S.: KET 02: An electron and ion telescope for an interstellar mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17863, https://doi.org/10.5194/egusphere-egu2020-17863, 2020.

D2832 |
Liu Yang, Linghua Wang, Qiugang Zong, Xiangqian Yu, Yongfu Wang, Weighing Shi, and Robert Wimmer-Schweingruber

The PKU energetic particle instrument (EPI) is designed to make measurements of the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range of 20–400 keV and ions from 20 keV–6 MeV. The output of front detectors is taken in anti-coincidence with center detectors, to achieve the low background. The magnet telescopes also employ the well-established dE/dx vs. total energy approach to determine the nuclear charge and mass of some ion species.

How to cite: Yang, L., Wang, L., Zong, Q., Yu, X., Wang, Y., Shi, W., and Wimmer-Schweingruber, R.: PKU Energetic Particle Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2043, https://doi.org/10.5194/egusphere-egu2020-2043, 2020.

D2833 |
Xiangqian Yu, Xin Huang, Linghua Wang, Weihong Shi, Yongfu Wang, Haobo Fu, and Zixuan Liu

The Solar Electron and Ion Telescope (SEIT), proposed by Peking University for a L1 non-spinning spacecraft mission, is designed to provide Omni-directional investigation of Solar energetic electrons and Ions with good time, energy and angular resolution. SEIT consists of multi group two dual double-ended magnet/foil particle telescopes which cleanly separate and measure electrons in the energy range from 50–400 keV and Ions from 60–7000 keV expected to be including protons, C and O. The multi group particle telescopes can cover the Omni-directional space. Each two dual double-ended magnet/foil particle telescopes set-up refers to the detector stack with view cones in two opposite directions: one side (electron side) is consisted of a 300um and a 500um Silicon detector whose distance is only 100um to chive a high performance, the 300um Silicon is on the front and covered by a 5um thin parylene foil to leave the electron spectrum essentially unchanged but stops low energy Ions, the other side (Ions side) is consisted of a 100um and a 500um Silicon detector whose distance is only 100um to chive a high performance and the front of the telescope is surrounded by a magnet to sweep away electrons but lets ions pass. The dead layer of the detector is only 100 Å and each detector is divided into five pixels to chive a high angular resolution. The time resolution is 1s. Simulation shows that the maximum counts of the 20 pixels can reach to 2452, while the minimum energy deposition of the 20 pixels is 300 keV. We now describe the design and GEANT4 simulation of SEIT.

How to cite: Yu, X., Huang, X., Wang, L., Shi, W., Wang, Y., Fu, H., and Liu, Z.: The GEANT4 simulation of PKU Solar Electron and Ions Telescope, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6657, https://doi.org/10.5194/egusphere-egu2020-6657, 2020.

D2834 |
Weihong Shi, Xiangqian Yu, Yongfu Wang, Linghua Wang, Xin Huang, and Zixuan Liu

The Energetic Particle Instrument (EPI), proposed by Peking University for a L1 mission, is designed to provide the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range from 20 to 400 keV and ions from 20 keV to 6 MeV.

The magnet of semi-conductor telescopes consists of four type 677H rare earth permanent magnets and a soft iron frame. Due to the high saturation polarization and high magnetic anisotropy of the Nd2Fe14B strongly magnetic matrix phase, this system can make the magnetic field strong enough to make the electrons deflected.

A frame made of iron-cobalt alloy VACOFLUX 50 will be able to combine two pairs of magnets and cause the magnetic field to decay rapidly in the far field. In this way, the two air gaps in the system can simultaneously provide a deflecting magnetic field for a pair of anti-parallel sensor systems.

How to cite: Shi, W., Yu, X., Wang, Y., Wang, L., Huang, X., and Liu, Z.: The Deflection Magnet Design for PKU Energetic Particle Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12082, https://doi.org/10.5194/egusphere-egu2020-12082, 2020.

D2835 |
Yongfu Wang, Qiugang Zong, Linghua Wang, Hongfei Chen, and Hong Zou

Substorm is the global disruptive activity in Earth’s magnetotail, including phenomena such as reconnection, plasmoid, flux rope, BBFs, energetic particle injection, and aurora etc. The ground based observations are often hard to determine the time sequences of substorm activities, while the satellite in-situ observations often cannot distinguish between temporal and spatial variations, therefore the global imaging observations are very useful in substorm studies. In this study we demonstrate the physical design of a grid-based energetic neutral atom (ENA) imager that can provide high temporal, spatial and energy resolution ENA imaging of Earth’s magnetotail. The ENA imager takes advantage of spatial Fourier modulation to the ENA fluxes to construct the ENA images, which is inspired by RHESSI. The physical design including imaging process, the charged particle reflector, and the ENA species discrimination etc. are described, along with the engineering progresses.

How to cite: Wang, Y., Zong, Q., Wang, L., Chen, H., and Zou, H.: A High Temporal, Spatial and Energy Resolution Grid-based Energetic Neutral Atom (ENA) Imager: the Physical Design, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13050, https://doi.org/10.5194/egusphere-egu2020-13050, 2020.

D2836 |
Siyu Song, Hongfei chen, Xiangqian Yu, and Qiugang Zong

In the study of internal charging of dielectrics inside the spacecraft, we mainly focus on the influence of conductivity of dielectrics induced by space radiation(Radiation Induced Conductivity), and regard the relative permittivity as constant. However, during the ground testing of dielectrics, we found that the relative permittivity of dielectrics decreased after being exposed to electron beams, thus affecting the electric field and the release of charge inside dielectrics. The relative permittivity can gradually returned to the initial state when the radiation stops. In the paper, we present the experiment result and try to give explanations on the mechanism behind this phenomenon.

How to cite: Song, S., chen, H., Yu, X., and Zong, Q.: The Influence of Space Radiation on the Relative Permittivity of Dielectrics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21360, https://doi.org/10.5194/egusphere-egu2020-21360, 2020.

D2837 |
Ao Chen, Chao Yue, Hongfei Chen, and Qiugang Zong

Ring curent is an important current system in the Earth's magnetosphere. Many charged particles, especially protons and oxygen ions, move around the Earth due to due to electromagnetic drifts, which forms the ring current. During the main phase of a magnetic storm, ring current will grow stronger while it will decay slowly during recover phase. It is thought that charge exchange is the main mechanism of ring current decay [Daglis et al., 1999]. Hereby we use charge exchange theories to calculate charge exchange lifetimes of protons and oxygen ions during recover phase of many storms. Meanwhile, data of RBSP has been used for fitting in order to get real lifetimes of  protons and oxygen ions. We compared the observed lifetimes with the theory prediction and find that  a. the two are close at high L(>4) values and low energy(<55keV) for protons, b. the two are similar in a wide energy(1~600keV) range but a relatively narrow L(different at different energies) range, c. day or night make little difference on the comparison results.

How to cite: Chen, A., Yue, C., Chen, H., and Zong, Q.: Ring current decay during storm recover phase: RBSP Observation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21672, https://doi.org/10.5194/egusphere-egu2020-21672, 2020.