Small-scale magnetic field fluctuations in the low-/mid-latitude nighttime ionosphere

Abstract:

The nighttime low-/mid-latitude ionosphere hosts a variety of plasma density irregularities, such as equatorial plasma bubbles (EPBs), low-latitude blobs, and medium-scale traveling ionospheric disturbances (MSTIDs). These irregularities act as sources of small-scale current systems. Plasma pressure gradient across the irregularity boundaries generates currents flowing along the boundary surface. These currents enforce or weaken background geomagnetic field strength without divergence (diamagnetic effect). On the other hand, large-scale currents flowing in the background plasma across magnetic field lines can diverge/converge at the plasma density depletion/enhancement, respectively. The current divergence results in field-aligned currents (FACs), which generates magnetic field deflections perpendicular to the background field. All these small-scale current systems make conspicuous changes in the magnetic field observed by Low-Earth-Orbit (LEO) satellites crossing the currents sheets. In this presentation we briefly review the advances since year 2000 in the field of current systems related to plasma irregularities in the nighttime low-/mid-latitude ionosphere.