Precipitating Particle Fluxes Research Articles

Impact of interplanetary shock on nitric oxide cooling emission: A superposed epoch study

The impact of interplanetary (IP) shock on Nitric Oxide (NO) 5.3 µm cooling emission is studied during geomagnetic quiet periods. The Active Magnetosphere and Planetary Electrodynamics Response Experiment measurements of field-aligned-currents intensify during IP shock with a relatively higher magnitude in southern hemisphere as compared to the northern hemispheric counterpart. The Defense Meteorological Satellite Program spacecraft observations displayed an early and strong enhancement in the precipitating particle flux of energy less than 1 keV. The particle flux of higher energy responds at later time. The NO density exhibited a significant, pre-event increase by an order of magnitude due to low-energy particle precipitation. The thermospheric temperature increased by about 100 K at 400 km. The superposed epoch analysis study revealed a linear enhancement in SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) measurements of NO cooling emission onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite due to the prompt increase in particle precipitations and thermospheric temperature triggered by IP shock.

Time‐Dependent Inversion of Energetic Electron Precipitation Spectra From Ground‐Based Incoherent Scatter Radar Measurements

AbstractIn the D‐region, the ionization rate cannot be detected directly with any known measurement technique, therefore it must be estimated. Starting from space‐based measurements of precipitating particle flux, we estimate the ionization rate in the atmosphere using the Electron Precipitation Monte Carlo transport method. This ionization rate is used to calculate the expected electron density in the D‐region with the Glukhov‐Pasko‐Inan five species (GPI5) atmospheric chemistry model. We then compare the simulated electron density with that measured by the Poker Flat Incoherent Scatter Radar (PFISR). From ground‐based radar measurements of electron density enhancements due to sub‐relativistic and relativistic electron precipitation, we present a method to extract the ionization rate altitude profiles using inverse theory. We use this estimation of ionization rate to find the energy distribution of the precipitating particles. With this inverse method, we are able to link ground measurements of electron density to the precipitating flux in a time dependent manner and with uncertainty in the inverted parameters. The method was tested on synthetic data and applied to specific PFISR data sets. The method is able to retrieve the ionization rate altitude profiles that, when forward modeled, return the expected electron densities within ∼7% error as compared to the PFISR data. For the case presented here, the arbitrary energy distribution inversion results are comparable in magnitude and shape to those presented in Turunen et al. (2016, https://doi.org/10.1002/2016jd025015) for the inversion of a single event of pulsating aurora observed by EISCAT.

Energy Input of EUV, Solar Wind, and SEPs at Mars: MAVEN Observations During Solar Minimum

AbstractSolar extreme ultraviolet (EUV) radiation, the solar wind, and solar energetic particles (SEPs) are variable sources of ionization and heating to the Martian atmosphere. Mars Atmosphere Volatile Evolution’s (MAVEN's) elliptical orbit provides a means to characterize these solar drivers immediately upstream of Mars. We have calculated the energy fluxes of EUV, solar wind, and SEPs while MAVEN is outside of the Martian induced magnetosphere. By time‐averaging observations over 2–5 month periods, we reduced short‐term variability to resolve seasonal and solar cycle trends. For the duration spanning the declining phase of solar cycle 24 and three Mars years, the calculated energy fluxes in units of 109 eV/cm2/s were 650–1,400 for EUV, 77–180 for solar wind ions, 2.4–7.4 for solar wind electrons, 0.01–2.7 for SEP ions, and 0–0.4 for SEP electrons. We estimated the fraction of these energy fluxes that would reach the atmosphere and determined that precipitating particle fluxes on the dayside would need to exceed 1012 eV/cm2/s to compare to EUV. We also predicted that SEPs may impart as much or more energy flux than solar wind electrons on the nightside during periods of strong and weak coronal mass ejection activity. We then discussed and decoupled seasonal variation from the solar drivers to reveal trends and outliers as a function of solar cycle. Finally, we compared MAVEN observations during a weak solar cycle to prior estimates of EUV, solar wind, and SEPs from the young sun, and identified times when MAVEN‐observed peak energy fluxes were close to the steady‐state energy fluxes of the ancient solar system.

First 3D hybrid-Vlasov global simulation of auroral proton precipitation and comparison with satellite observations

The precipitation of charged particles from the magnetosphere into the ionosphere is one of the crucial coupling mechanisms between these two regions of geospace and is associated with multiple space weather effects, such as global navigation satellite system signal disruption and geomagnetically induced currents at ground level. While precipitating particle fluxes have been measured by numerous spacecraft missions over the past decades, it often remains difficult to obtain global precipitation patterns with a good time resolution during a substorm. Numerical simulations can help to bridge this gap and improve the understanding of mechanisms leading to particle precipitation at high latitudes through the global view they offer on the near-Earth space system. We present the first results on auroral (0.5–50 keV) proton precipitation within a 3-dimensional simulation of the Vlasiator hybrid-Vlasov model. The run is driven by southward interplanetary magnetic field conditions with constant solar wind parameters. We find that on the dayside, cusp proton precipitation exhibits the expected energy–latitude dispersion and takes place in the form of successive bursts associated with the transit of flux transfer events formed through dayside magnetopause reconnection. On the nightside, the precipitation takes place within the expected range of geomagnetic latitudes, and it appears clearly that the precipitating particle injection is taking place within a narrow magnetic local time span, associated with fast Earthward plasma flows in the near-Earth magnetotail. Finally, the simulated precipitating fluxes are compared to observations from Defense Meteorological Satellite Program spacecraft during driving conditions similar to those in the simulation and are found to be in good agreement with the measurements.

Diffuse Auroral Electron and Ion Precipitation Effects on RCM-E Comparisons With Satellite Data During the 17 March 2013 Storm.

Effects of scattering of electrons from whistler chorus waves and of ions due to field line curvature on diffuse precipitating particle fluxes and ionospheric conductance during the large 17 March 2013 storm are examined using the self-consistent Rice Convection Model Equilibrium (RCM-E) model. Electrons are found to dominate the diffuse precipitating particle integrated energy flux, with large fluxes from ~21:00 magnetic local time (MLT) eastward to ~11:00 MLT during the storm main phase. Simulated proton and oxygen ion precipitation due to field line curvature scattering is sporadic and localized, occurring where model magnetic field lines are significantly stretched on the night side at equatorial geocentric radial distances r 0 ≳8 R E and/or at r 0 ~5.5 to 6.5 R E from dusk to midnight where the partial ring current field has perturbed the magnetic field. The precipitating protons likewise contribute sporadically to the storm time Hall and Pedersen conductance in localized regions whereas the precipitating electrons are the dominate storm time contributor to enhanced Hall and Pedersen conductance at auroral magnetic latitudes on the night and morning side. The RCM-E model can reproduce general features of the Van Allen Probe/MagEIS observed trapped electron differential flux spectrograms over energies of ~37 to 150 keV. The simulations with a parameterized electron loss model also reproduce reasonably well the storm time Defense Meteorological Satellite Program integrated electron energy flux at 850 km at satellite crossings from predawn to midmorning. However, model-data agreement is not as good from dusk to premidnight where there are large uncertainties in the electron loss model.

Impact of Precipitating Electrons and Magnetosphere‐Ionosphere Coupling Processes on Ionospheric Conductance

AbstractModeling of electrodynamic coupling between the magnetosphere and ionosphere depends on accurate specification of ionospheric conductances produced by auroral electron precipitation. Magnetospheric models determine the plasma properties on magnetic field lines connected to the auroral ionosphere, but the precipitation of energetic particles into the ionosphere is the result of a two‐step process. The first step is the initiation of electron precipitation into both magnetic conjugate points from Earth's plasma sheet via wave‐particle interactions. The second step consists of the multiple atmospheric reflections of electrons at the two magnetic conjugate points, which produces secondary superthermal electron fluxes. The steady state solution for the precipitating particle fluxes into the ionosphere differs significantly from that calculated based on the originating magnetospheric population predicted by magnetohydrodynamic and ring current kinetic models. Thus, standard techniques for calculating conductances from the mean energy and energy flux of precipitating electrons in model simulations must be modified to account for these additional processes. Here we offer simple parametric relations for calculating Pedersen and Hall height‐integrated conductances that include the contributions from superthermal electrons produced by magnetosphere‐ionosphere‐atmosphere coupling in the auroral regions.

The Impact of Energetic Particle Precipitation on Mesospheric OH – Variability of the Sources and the Background Atmosphere

AbstractUsing a new analysis technique, we estimate the precipitating particle fluxes measured by the Medium Energy Proton and Electron Detector on the National Oceanic and Atmospheric Administration Polar Orbiting Environmental Satellites. These fluxes are used to quantify the direct impact of energetic particle precipitation (EPP) on mesospheric hydroxyl (OH) measured from the Aura satellite during 2005–2009 in the Northern Hemisphere, covering the declining and minimum phase of solar cycle 23. Using multiple linear regression of nighttime OH volume mixing ratio with temperature, geopotential height, water vapor (H2O) volume mixing ratio, Lyman‐alpha (Ly‐α) radiation, and particle energy deposition, we account for the background variability and hence the EPP impact independent of season and other short‐term variability. We investigate the relative importance of solar proton events, energetic electron precipitation and the background to OH variability. The background dominates over EPP above 70‐km altitude. Below 70 km, EPP dominates. The maximum EPP contribution is 44% and 34% in the geographic and corrected geomagnetic (CGM) settings respectively at 67 km. Protons dominate over electrons at mesospheric altitudes with maximum contributions of 43% and 32% at 67 km in the geographic and CGM settings, respectively. In a CGM setting, the electrons contribution is comparable to that of protons above 70 km, with a maximum contribution of 11% at 75 km. Since the period investigated is during relatively low solar activity, these results represent a lower estimate of the general EPP contribution to OH variability.

Dynamics of ionospheric disturbances during the 17–19 March 2015 geomagnetic storm over East Asia

Based on vertical sounding data from nine ionosondes located at 19–66°N, 100–130°E we investigated the latitude-temporal dynamics of ionospheric disturbances during the 17–19 March 2015 severe two-step geomagnetic storm, and compared it with temporal dynamics of total electron content (TEC) profiles along 120°E. The phenomena that accompanied the main and early recovery storm phases were in particular focused on in this study. The distinct storm-related ionospheric disturbances began 2.5, 4 and 5h after onset of the storm main phase at subauroral, middle and low latitudes, respectively. To clarify the main mechanisms causing the disturbances at different latitudes we compared the changes in ionospheric parameters and TEC profiles with changes in the northern polar cap index and geomagnetic field in the vicinity of 120°E. The equatorward shift of the main ionospheric trough (MIT) and diffuse precipitations zone accompanied by an increase in precipitating particle flux was found to have a substantial influence on the subauroral ionosphere during the main and early recovery phases. The thermosphere Joule heating due to westward and polarized jets led to an increase in neutral wind velocity and generation of disturbed dynamo electric field. The strengthened wind was the main reason of the positive ionospheric disturbance observed at middle latitudes in the evening on 17 March. The further enhancement of magnetospheric convection caused the displacement of MIT and its associated negative ionospheric disturbance to middle latitudes. At low latitudes superposition of prompt penetration and disturbed dynamo electric fields play the decisive role in the ionosphere behavior till the end of the early recovery phase.

Use of POES SEM‐2 observations to examine radiation belt dynamics and energetic electron precipitation into the atmosphere

The coupling of the Van Allen radiation belts to the Earth's atmosphere through precipitating particles is an area of intense scientific interest. Currently, there are significant uncertainties surrounding the precipitating characteristics of medium energy electrons (>20 keV), and even more uncertainties for relativistic electrons. In this paper we examine roughly 10 years of measurements of trapped and precipitating electrons available from the Polar Orbiting Environmental Satellites (POES)/Space Environment Monitor (SEM‐2), which has provided long‐term global data in this energy range. We show that the POES SEM‐2 detectors suffer from some contamination issues that complicate the understanding of the measurements, but that the observations provide insight into the precipitation of energetic electrons from the radiation belts, and may be developed into a useful climatology for medium energy electrons. Electron contamination also allows POES/SEM‐2 to provide unintended observations of >700 keV relativistic electrons. Finally, there is an energy‐dependent time delay observed in the POES/SEM‐2 observations, with the relativistic electron enhancement (electrons >800 keV) delayed by approximately one week relative to the >30 keV electron enhancement, probably due to the timescales of the acceleration processes. Observations of trapped relativistic electron fluxes near the geomagnetic equator by GOES show similar delays, indicating a “coherency” to the radiation belts at high and low orbits, and also a strong link between trapped and precipitating particle fluxes. Such large delays should have consequences for the timing of the atmospheric impact of geomagnetic storms.

The influence of geomagnetic activity on mesospheric summer echoes in middle and polar latitudes

Abstract. The dependence of mesospheric VHF radar echoes during summer months on geomagnetic activity has been investigated with observation data of the OSWIN radar in Kühlungsborn (54° N) and of the ALWIN radar in Andenes (69° N). Using daily mean values of VHF radar echoes and of geomagnetic activity indices in superimposed epoch analyses, the comparison of both data sets shows in general stronger radar echoes on the day of the maximum geomagnetic activity, the maximum value one day after the geomagnetic disturbance, and enhanced radar echoes also on the following 2–3 days. This phenomenon is observed at middle and polar latitudes and can be explained by precipitating particle fluxes during the ionospheric post storm effect. At polar latitudes, the radar echoes decrease however during and one day after very strong geomagnetic disturbances. The possible reason of this surprising effect is discussed.

Study of plasma pressure distribution in the inner magnetosphere using the low altitude satellite data and its relevance for magnetospheric dynamics

Plasma pressure distribution in the inner magnetosphere is one of the key parameters for understanding the main magnetospheric processes including geomagnetic storms and substorms. However, the pressure profiles obtained from in-situ particle measurements by the high-altitude satellites inside the plasma sheet do not allow tracking the pressure variations related to the magnetospheric dynamics, because time interval needed to do this generally exceeds the characteristic times of the main magnetospheric processes. On the contrary, fast movement of low-altitude satellites makes it possible to restore quasi-instantaneous profiles of plasma pressure along the satellite trajectory, using the precipitating particle flux data in the regions of isotropic plasma pressure. It was found that during quiet geomagnetic conditions profiles obtained from low-altitude and high-altitude satellites coincide. Nevertheless, the plasma pressure profiles change significantly during the development of storms and substorms, that indicates possibility of the interchange (storm) or modified interchange (substorm) instability development.

The reconnection site of temporal cusp structures

The strong precipitating particle flux in the cusp regions is the consequence of magnetic reconnection between the interplanetary magnetic field and the geomagnetic field. Magnetic reconnection is thought to be the dominant process for mass, energy, and momentum transfer from the magnetosheath into the magnetosphere. Observations of downward precipitating cusp ions by polar orbiting satellites are instrumental in unlocking many questions about magnetic reconnection, e.g., their spatial and temporal nature and the location of the reconnection site at the magnetopause. In this study we combine cusp observations of structures in the precipitating ion‐energy dispersion by the Cluster satellites with Super Dual Auroral Radar Network radar observations to distinguish between the temporal and spatial magnetic reconnection processes at the magnetopause. The location of the cusp structures relative to the convection cells is interpreted as a temporal phenomenon caused by a change in the reconnection rate at the magnetopause. The 3‐D plasma observations of the Cluster Ion Spectrometry instruments onboard the Cluster spacecraft also provide the means to estimate the location of the reconnection site. While an earlier study of a spatial cusp structure event revealed bifurcated reconnection locations in different hemispheres as origins for the precipitating ions creating the cusp structures, the same method applied to the temporal cusp structures in this study shows only a single tilted reconnection line close to the subsolar point. Tracing the distance to the reconnection site provides not only the location of the reconnection line but can also be used to distinguish between spatial and temporal cusp structures.

Radial distribution of the inner magnetosphere plasma pressure using low-altitude satellite data during geomagnetic storm: The March 1–8, 1982 event

Plasma pressure distribution in the inner magnetosphere is one of the key parameters for understanding the main magnetospheric processes including geomagnetic storms and substorms. However, the pressure profiles obtained from in-situ particle measurements by the high-altitude satellites inside the plasma sheet and other regions of the magnetosphere do not allow tracking the pressure variations related to the storms and substorms, because a time interval needed to do this generally exceeds the characteristic times of them. On the contrary, fast movement of low-altitude satellites makes it possible to retrieve quasi-instantaneous radial or azimuthal profiles of plasma pressure along the satellite trajectory, using the precipitating particle flux data in the regions of isotropic plasma pressure. For this study, we used the low-altitude polar-orbiting Aureol-3 satellite data for plasma pressure estimation, and the IGRF, Tsyganenko 2001 and Tsyganenko 2004 storm time geomagnetic field models for the pressure mapping into the equatorial plane, and for the evaluation the corresponding volume of the magnetic flux tube. It was found that during quiet geomagnetic condition the radial pressure profiles obtained coincide with the profiles, obtained previously from the high-altitude measurements. On the contrary, the plasma pressure profiles change significantly during the development of storms and substorms. Nevertheless, three geomagnetic field models gave significantly different geomagnetic field profiles, those points out the necessity to develop a magnetically self-consistent model for description of the inner magnetosphere geomagnetic field. However, the common features observed for all models are: during geomagnetic storm the plasma pressure profiles became sharper; the position of the maximum of plasma pressure corresponds to expected one for given D st minimum; the maximum value of inner magnetosphere static pressure correlates with the solar wind dynamic pressure. Increase in the plasma pressure profiles indicates the possibility to consider the interchange instability as one of important factors for the development of the main phase of geomagnetic storm.

TRANS4: a new coupled electron/proton transport code – comparison to observations above Svalbard using ESR, DMSP and optical measurements

Abstract. We present for the first time a numerical kinetic/fluid code for the ionosphere coupling proton and electron effects. It solves the fluid transport equations up to the eighth moment, and the kinetic equations for suprathermal particles. Its new feature is that for the latter, both electrons and protons are taken into account, while the preceding codes (TRANSCAR) only considered electrons. Thus it is now possible to compute in a single run the electron and ion densities due to proton precipitation. This code is successfully applied to a multi-instrumental data set recorded on 22 January 2004. We make use of measurements from the following set of instruments: the Defence Meteorological Satellite Program (DMSP) F-13 measures the precipitating particle fluxes, the EISCAT Svalbard Radar (ESR) measures the ionospheric parameters, the thermospheric oxygen lines are measured by an all-sky camera and the Hα line is given by an Ebert-Fastie spectrometer located at Ny-Ålesund. We show that the code computes the Hα spectral line profile with an excellent agreement with observations, providing some complementary information on the physical state of the atmosphere. We also show the relative effects of protons and electrons as to the electron densities. Computed electron densities are finally compared to the direct ESR measurements.

The auroral and ionospheric flow signatures of dual lobe reconnection

Abstract. We present the first substantial evidence for the occurrence of dual lobe reconnection from ionospheric flows and auroral signatures. The process of dual lobe reconnection refers to an interplanetary magnetic field line reconnecting with lobe field lines in both the northern and southern hemispheres. Two bursts of sunward plasma flow across the noon portion of the open/closed field line boundary (OCB), indicating magnetic flux closure at the dayside, were observed in SuperDARN radar data during a period of strongly northward IMF. The OCB is identified from spacecraft, radar backscatter, and auroral observations. In order for dual lobe reconnection to take place, we estimate that the interplanetary magnetic field clock angle must be within ±10° of zero (North). The total flux crossing the OCB during each burst is small (1.8% and 0.6% of the flux contained within the polar cap for the two flows). A brightening of the noon portion of the northern auroral oval was observed as the clock angle passed through zero, and is thought to be due to enhanced precipitating particle fluxes due to the occurrence of reconnection at two locations along the field line. The number of solar wind protons captured by the flux closure process was estimated to be ~2.5×1030 (4 tonnes by mass), sufficient to populate the cold, dense plasma sheet observed following this interval.

Study of plasma pressure distribution in the inner magnetosphere using low-altitude satellites and its importance for the large-scale magnetospheric dynamics

Plasma pressure distribution in the inner magnetosphere is one of the key parameters for understanding main processes of the magnetospheric dynamics including geomagnetic substroms. However, the pressure profiles obtained from in situ measurements by the high-altitude satellites do not allow the tracking of the magnetospheric dynamics, because a time necessary to obtain these profiles (hours) generally exceeds the characteristic times of the main magnetospheric processes (minutes or less). On contrary, fast movement of low-altitude satellites makes it possible to obtain quasi-instantaneous profiles of plasma pressure along the satellite trajectory – radial or azimuthal, depending on the satellite orbit. Precipitating particle fluxes, measured by the low-altitude Aureol-3 satellite were used. Mapping into the equatorial plane and determination of a volume of the magnetic flux tube were made using the Tsyganenko 96 and 01 geomagnetic field models. Study of radial plasma gradients showed that the inner magnetosphere is stable for development of flute (interchange) instability. Modified interchange instability related to azimuthal plasma pressure gradients and field-aligned currents in equilibrium was proposed as a source of substorm expansion phase onset. It can develop when the density of the field-aligned current reaches a definite threshold value. The growth rate of the instability is higher in the region of upward field-aligned current, where the existing field-aligned potential drop leads to the magnetosphere–ionosphere decoupling.

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Abstract. We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001) survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992). The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV), we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence the location and behaviour of the plasma populations in the magnetosphere. Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; magnetospheric configuration and dynamic)

Azimuthal plasma pressure reconstructed by using the Aureol-3 satellite data during quiet geomagnetic conditions

The azimuthal distribution of magnetospheric plasma pressure was studied using the precipitating particle fluxes observed by the low-altitude polar-orbiting Aureol-3 satellite. The data from the 18 March 1982 event was used to calculate the pressure along the satellite trajectory during quiet geomagnetic conditions. The magnetic flux tube volumes for the field-lines, corresponding to the points of measurement at the satellite trajectory, were calculated by using Tsyganenko 96 magnetic-field model. The gradients of the plasma pressure along the isosurfaces of the volume of the magnetic flux tube per unit flux were estimated, and the field-aligned currents were calculated assuming that the condition of the magnetostatic equilibrium is valid. The results obtained were compared with the [J. Geophys. Res. 81 (13) (1976) 2165] field-aligned current distribution.

Mapping of the cusp plasma precipitation on the surface of Mercury

The presence of a magnetosphere around Mercury plays a fundamental role on the way the solar wind plasma interacts with the planet. Since the observations suggest that Mercury should occupy a large fraction of its magnetosphere and because of lack of an atmosphere, significant differences in solar wind-magnetosphere coupling are expected to exist with respect to the Earth case. On the basis of a modified Tsyganenko T96 model we describe the geometry of the magnetic field that could characterize Mercury, and its response to the variations of the impinging solar wind and of the interplanetary magnetic field. The investigation is focused on the shape and dimension of the open magnetic field regions (cusps) that allow the direct penetration of magnetosheath plasma through the exosphere of Mercury, down to its surface. The precipitating particle flux and energy are evaluated as a function of the open field line position, according to different solar wind conditions. A target of this study is the evaluation of the sputtered particles from the crust of the planet, and their contribution to the exospheric neutral particle populations. Such estimates are valuable in the frame of a neutral particle analyser to be proposed on board of the ESA/BepiColombo mission.

Construction of a particle climatology for the study of the effects of solar particle fluxes on the atmosphere

In an investigation of the atmospheric effects of particle input, we are currently developing a particle climatology built using the UARS (Upper Atmosphere Research Satellite) particle database. UARS operates in a circular 585 km orbit and makes differential energy per unit charge measurements of electrons and positive ions in the range of a few eV to several MeV. The climatology is an empirical model that enables the user to obtain average spectral characteristics, precipitating particle fluxes, and ionization rate profiles as functions of latitude, local time, and activity level. To further the goals of Working Group 1 of the International Solar Cycle Study (ISCS), we propose the construction of such a particle climatology. We suggest the UARS particle climatology as a starting point, to be augmented by additional low-altitude particle data. In this paper we describe the development of the current climatology, show how it will be augmented to produce an improved ISCS climatology, and illustrate how this climatology will be used to carry out the objectives of the ISCS.