Field-aligned current associated with low-latitude plasma blobs as observed by the CHAMP satellite

Abstract. Here we give two examples of low-latitude plasma blobs accompanied by linearly polarized perpendicular magnetic deflections which imply that associated field-aligned currents (FACs) have a 2-D sheet structure located at the blob walls. The estimated FAC density is of the order of 0.1 μA/m 2 . The direction of magnetic deflections points westward of the magnetic meridian and there is a linear correlation between perpendicular and parallel variations. All these properties are similar to those of equatorial plasma bubbles (EPBs). According to CHAMP observations from August 2000 to July 2004, blobs show except for these two good examples no clear signatures of 2-D FAC sheets at the walls. Generally, perpendicular magnetic deflections inside blobs are weaker than inside EPBs on average. Our results are consistent with existing theories: if a blob exists, (1) a significant part of EPB FAC will be closed through it, exhibiting similar perpendicular magnetic deflection inside EPBs and blobs, (2) the FAC closure through blobs leads to smaller perpendicular magnetic deflection at its poleward/downward side, and (3) superposition of different FAC elements might result in a complex magnetic signature around blobs.

[1]  L. Paxton,et al.  The temporal evolution of the large equatorial plasma depletions observed during the 29–30 October 2003 storm , 2010 .

[2]  H. Lühr,et al.  The characteristics of field-aligned currents associated with equatorial plasma bubbles as observed by the CHAMP satellite , 2009 .

[3]  M. Mendillo,et al.  Brightening of 630.0 nm equatorial spread‐F airglow depletions , 2009 .

[4]  J. Huba,et al.  Three‐dimensional modeling of equatorial spread F airglow enhancements , 2009 .

[5]  R. Heelis,et al.  Formation of a plasma depletion shell in the equatorial ionosphere , 2009 .

[6]  H. Lühr,et al.  Magnetic signatures and conjugate features of low‐latitude plasma blobs as observed by the CHAMP satellite , 2008 .

[7]  M. Parrot,et al.  Filamentary Alfvénic structures excited at the edges of equatorial plasma bubbles , 2007 .

[8]  T. Yokoyama,et al.  Plasma blobs and irregularities concurrently observed by ROCSAT‐1 and Equatorial Atmosphere Radar , 2006 .

[9]  Georgios Balasis,et al.  Magnetic signatures of equatorial spread F as observed by the CHAMP satellite , 2006 .

[10]  K. Min,et al.  Global distribution of equatorial plasma bubbles in the premidnight sector during solar maximum as observed by KOMPSAT‐1 and Defense Meteorological Satellite Program F15 , 2005 .

[11]  H. Takahashi,et al.  Plasma blobs observed by ground‐based optical and radio techniques in the Brazilian tropical sector , 2004 .

[12]  K. Min,et al.  Plasma blob events observed by KOMPSAT‐1 and DMSP F15 in the low latitude nighttime upper ionosphere , 2003 .

[13]  R. Heelis,et al.  Plasma Density Enhancements Associated With Equatorial Spread F , 2003 .

[14]  J. Makela,et al.  Field‐aligned 777.4‐nm composite airglow images of equatorial plasma depletions , 2003 .

[15]  G. K. Mukherjee.  Studies of equatorial F-region depletions and dynamics using multiple wavelength nightglow imaging , 2003 .

[16]  L. C. Gentile,et al.  DMSP observations of equatorial plasma bubbles in the topside ionosphere near solar maximum , 2001 .

[17]  W. J. Burke,et al.  A transmission line analogy for the development of equatorial ionospheric bubbles , 2000 .

[18]  P. J. Sultan,et al.  Linear theory and modeling of the Rayleigh‐Taylor instability leading to the occurrence of equatorial spread F , 1996 .

[19]  W. J. Burke,et al.  Equatorial bubbles updrafting at supersonic speeds , 1992 .

[20]  M. Mendillo,et al.  Geometry of depleted plasma regions in the equatorial ionosphere , 1983 .

[21]  H. Booker,et al.  Scattering of radio waves by the F-region of the ionosphere , 1938 .

[22]  M. Hairston,et al.  Statistical description of low-latitude plasma blobs as observed by DMSP F15 and KOMPSAT-1 , 2008 .

[23]  R. Heelis,et al.  Global Distribution of Density Irregularities in the Equatorial Ionosphere , 1998 .

[24]  Hiroshi Oya,et al.  Occurrence Characteristics of Low Latitude Ionosphere Irregularities Observed by Impedance Probe on Board the Hinotori Satellite , 1986 .

[25]  Hiroshi Oya,et al.  Observation of Low Latitude Ionosphere by the Impedance Probe on Board the Hinotori Satellite , 1986 .

[26]  R. Tsunoda,et al.  Control of the seasonal and longitudinal occurrence of equatorial scintillations by the longitudinal gradient in integrated E region Pedersen conductivity , 1985 .