The Pattern of By Deflections Produced from Field-Aligned Currents Earthward of the Activation Source in the Earth’s Magnetosphere

Abstract

In this investigation effort, we eventually infer that the overall quadrapole pattern of B y deflections, in the vicinity of a source in the Earth’s magnetotail, is most likely due to field aligned currents (FACs) and not to Hall currents associated with an X-type collisionless reconnection. This categorically expressed statement is based upon sufficient observational evidence tightly associated with our own suggested model and the preceded works of the same author. Using representative events measured by satellite, our main aim is to describe the nature of the fundamental mechanism determining the polarity of the B y deflections associated with intense earthward ionplasma flows. A major finding is that we either observe magnetic flux rope (MFR) like structures (that is, entities having all the morphological features of ropes; i.e. , a dipolar signature of B z occurring simultaneously with peaked B y and B total deflections) or mere B y deflections, however, the sign for all these (B y deflections) is always determined by the satellite placement in north (positive) or south (negative) plasma sheet. Therefore, the MFR-like structures located earthward of the source are most likely pseudo-MFRs; there is neither a tubular topology nor an axial magnetic field, the B y deflections are produced by FACs. According to the presented model, a fundamental concept is that both ions and electrons are simultaneously accelerated at the source site; in turn, the earthward streaming electrons (ions) form a bifurcated electron (ion) FAC just outside the electron diffusion region-EDR (IDR). In this way, inside the IDR (and earthward of the source) positive (negative) B y deflections in north (south) plasma sheet (PS) are produced due to FACs, and not to (inward) Hall currents as in the context of an X-line. Moreover, the ions form an “ion jet” within the IDR, while just outside this region they produce positive (negative) B y deflections in north (south) PS caused by ion FACs. The ion jet in the IDR is enveloped by the bifurcated electron FAC. Eventually, although the resulting pattern of B y deflections, due to both electron and ion FACs, is apparently the same with that resulting from Hall currents (in the X-line model), the underlying natural processes are, however, radically different. Certainly, the dominant “spatial entity” within the IDR is the ion jet-current (and not the Hall-electron current). Additional implications of the ion jets are also discussed.