L. A. Avanov

Signatures of impulsive convection in the magnetospheric lobes

We analyze the injections of tailward flowing O+ ions measured by PROGNOZ-8 in the magnetospheric lobes using three-dimensional single-particle codes. These injections are shaped as “inverted Vs” and unexpectedly well correlated with AE variations during a time interval of about 7 hours. Such a correlation leads us to consider the effect of transient intensification of the large-scale magnetospheric convection. Using a simple model of time-varying electric field, we show that the source of the O+ lies near the dayside cusp. This source extends over a narrow (a few degrees) latitudinal interval in the vicinity of the last closed field line, likely involving ions expelled into the magnetosphere after being transversely accelerated. We demonstrate that, downstream of the ejection site, impulsive convection leads to prominent structuring of the tailward streaming particles with abrupt energy variations on small length scales. A good agreement is obtained between the numerical results and the observations which supports our impulsive convection based interpretation framework.

Observation of Isolated Structures of the Low Latitude Boundary Layer with the INTERBALL/Tail Probe

Abstract. We analyze the structure of magnetospheric tran- sients observed at the dusk-side low-latitude magnetopause with the Interball Tail Probe. Ion and magnetic field meas- urements are used to investigate one particular transient in more detail. This transient has distinct non-symmetric struc- ture with the plasma characteristics and the flow properties of the leading part of the transient being quite different from those in the trailing part of the transient. The region separat- ing these two parts corresponds to the change of the sign in the Bn component. These observations support an earlier con- clusion that some plasma irregularities within the Low Lati- tude Boundary Layer (LLBL), formed as a result of sporadic reconnection, disconnect from the magnetopause, propagate and dissipate in the magnetosphere, and form what we call Disconnected Magnetosheath Transfer Events (DMTEs). Introduction Flux Transfer Events (FTE) with bipolar Bn signatures, discovered by Russell and Elphic [1978], are identified as re- connected flux tubes resulting from sporadic and localized re- connection. The occurrence of dayside FTEs is strongly cor- related with southward magnetosheath fields, consistent with dayside magnetic merging. Both magnetosheath and magne- tospheric FTEs contain magnetosphere-like and magne- tosheath-like plasmas [Paschmann et al., 1982, Thomsen et al., 1987] and display unique ion composition [Klumpar et al., 1990]. Several regions within FTEs have been identified: the reconnected flux tube and its associated external perturba- tions [Russell and Elphic, 1978], and, more recently, the fuzzy region between the open flux tube and the external perturbation [Rijnbeek et al., 1987]. Farrugia et al. [1988] de- fined four distinct nested regions in an FTE: a disturbed mag- netospheric region, the plasma mixing region, the magne- tosheath-like region (more isotropic and less dense plasma than in the magnetosheath), and the central region where the plasma is indistinguishable from the magnetosheath plasma. These regions are most easily distinguished by the ratio of the plasma to the magnetic field pressure, [3. Smith and Owen [1992] found D-shaped ion distributions in magnetosheath- like and central regions of the same event, caused by a paral-

HFA-like signatures observed with interball-tail spacecraft

We analyze HFAs observed with Interball-Tail in 1996. They are distinguished by a rotation of the magnetic field, by associated change in the shock regime from quasi-perpendicular to quasi-parallel and by a stronger flow deflection than at the bow shock. The magnetic field within an HFA is strongly varying, and its magnitude is often comparable to the solar wind value or less. Temperature jumps at HFAs are usually a factor of 2 higher, and the number density jumps are a factor of 2 lower than at the shock transition. Shock-like structure is frequently seen in the sunward part of an HFA and less frequently seen in the earthward part. Double (non-symmetric) structure is often seen in plasma parameters with a more isotropic velocity distribution in the sunward part of an HFA. A region with a cold ion component propagating antisunward separates these parts. Two ion components are usually seen inside an HFA, one of which seems to be a diluted and/or heated solar wind beam, and another which resembles diffuse u...

INTERBALL tail observations of dayside magnetopause oscillations and simultaneous POLAR cusp measurements

On April 13, 1996, while Russias Interball Tail spacecraft was travelling through the dayside magnetosheath, NASAs Polar spacecraft traversed the northern cusp. Ob- served transients seen in the SCA-1 Interball Tail data are shown to be multiple crossings of the magnetopause. Analysis of the moments data from the SCA-1 instrument and magnetic field data from the MIF instrument on Interball Tail show quasi-periodic motion of the magnetopause. Simultaneous ob- servations of changes in the He2+/H + density ratio in the cusp by the Polar/TIMAS instrument show variations on the same time scale. We conclude that the variations in cusp data ob- served by Polar are the result of changes in the reconnection rate at the magnetopause and that these changes are associated with the magnetopause oscillations observed by Interball. neous measurements at the magnetopause, may well be the best approach to relating magnetopause oscillations to changes in the reconnection rate. In this paper, we present a propitious conjunction when Polar was in the cusp and Interball Tail was near the dayside magnetopause (Fig. 1). Changes in the reconnection rate, in- dicated by changes in the He2+/H + ratio in the cusp, were ac- companied by magnetopause oscillations on a similar time scale. While previous studies have suggested correlations between observations in the cusp and, for example, the loca- tion of the magnetopause, we present here direct simultaneous plasma observations in the two regions.

The 2π charged particles analyzer: All-sky camera concept and development for space missions

Increasing the temporal resolution and instant coverage of velocity space of space plasma measurements is one of the key issues for experimentalists. Today the top-hat plasma analyzer appears to be the favorite solution due to its relative simplicity and the possibility to extend its application by adding a mass-analysis section and an electrostatic angular scanner. Similarly, great success has been achieved in MMS mission using such multiple top-hat analyzers to achieve unprecedented temporal resolution. n nAn instantaneous angular coverage of charged particles measurements is an alternative approach to pursuing the goal of high time resolution. This was done with FONEMA 4-D and, to a lesser extent, by DYMIO instruments for Mars-96 and with the FIPS instrument for MESSENGER mission. In this paper we describe, along with precursors, a plasma analyzer with a 2π electrostatic mirror that was developed originally for the Phobos-Soil mission with a follow-up in the frame of the BepiColombo mission, and is under development for future Russian missions. Different versions of instrument are discussed along with their advantages and drawbacks.