Observations of low-energy electrons upstream of the Earth's bow shock

Abstract

Observations of electron fluxes with a lunar‐based electron spectrometer when the moon was upstream of the earth have shown that a subset of observed fluxes are strongly controlled by the interplanetary magnetic field (IMF) direction. The fluxes occur only when the IMF lines connect back to the earth's bow shock. Observed densities and temperatures were in the ranges 2–4 × 10−3 cm−3 and 1.7–2.8 × 106 °K. It is shown that these electrons can account for increases in effective solar wind electron temperatures on bow shock connected field lines, which have been observed previously by other investigators. It is further shown that if a model of the bow shock with an electrostatic potential barrier is assumed, the potential can be estimated to be 500 V.

Electron velocity distributions near collisionless shocks

“…The first attempt at a quantitative measure of the energy flux transported by these electrons posed difficulties in interpretation because it showed a substantial flux carried by electrons having energy above 10 keV yet the amount carried below 10 keV than that carried on average by the total (mostly (Ogilvie et al, 1971 (Ogilvie and Scudder, 1979) are of orAer 10-2 ergs '2 S-l, representing a significant energy loss to the plasma within the shock cm transition layer. Whereas the downstreaming heat flux has been observed throughout the magnetosheath (Reiff and Reasoner, 197S;Ogilvie and Scudder, 1979), the backstreaming heat flux has been observed as far upstream as the moon (-60 earth radii, Re, Reasoner, 1975) and the inner sun-earth LagKangian point (-26L Re, Feldman et al, 1982a).…”

Bow-shock-associated proton heating in the upstream solar wind

“…Several possibilities have been considered. The electrons might be leaking from the magnetosheath through a bow shock possessing a high electrostatic potential barrier [Reasoner, 1975], or they might become heated upstream of the shock by the mechanism of Montgomery and Fredricks [1971]. The latter process, however, has to take place inside region 1 with hydromagnetic waves present.…”

Statistical analysis of MMS observations of energetic electron escape observed at/beyond the dayside magnetopause

“…In an attempt to highlight the novelty of the statistical study presented here amidst the extremely rich history of the study of energetic electrons beyond the magnetopause, a substantial (but admittedly nonexhaustive) literature review is provided in section 1.1. It must be emphasized that this paper (and the review included) will focus specifically on observations of energetic (greater than tens of keV) electrons observed in the magnetosheath and upstream of the bow shock and is independent of the extremely rich literature regarding the well‐documented history of lower energy (eV to several keV) particles at/beyond the magnetopause [e.g., Freeman et al , ; Montgomery et al , ; Scarf et al , ; Hones et al , ; Scudder et al , ; Reasoner , ; Eastman et al , ; Cowley , ; Fuselier et al , , ; Lefebvre et al , ; Lee et al , , and references therein] and observations of escaping magnetospheric ions [e.g., West and Buck , ; Anagnostopoulos et al , ; Sibeck et al , , ; Zong et al , ; Eccles and Fritz , ; Kronberg et al , ; Westlake et al , , and references therein], upstream ion events [e.g., Asbridge et al , ; Lin et al , ; Scholer et al , , ; Desai et al , , and references therein], and shock‐related ion acceleration [e.g., Ipavich et al , ; Gosling , ; Armstrong et al , ; Forman and Webb , ; Scholer , ; Thomsen , ; Sibeck et al , ; Burgess et al , ; Lee et al , , and references therein]. We focus here on electrons because ions have a broader array of escape mechanisms [ Mauk et al , ] that make their study substantially more complex.…”