Characteristics of Electric Currents and Fields Observed by MMS in the Magnetotail Plasma Sheet during Quiet and Active Periods

The present work was to figure out whether intense current structures are formed in the quiet Plasma Sheet (PS) of the Earth’s magnetotail, or whether they are observed only in the presence of Bursty Bulk Flows (BBFs). We had statistically analyzed absolute value of electric current density | j | , the magnitude of the nonideal electric field ( E 1pt ' = E + [ v_e × B ] , where v_e is electron bulk velocity, B and E are magnetic and observed electric fields, respectively) and the energy conversion rate ( j · E 1pt ' ) observed by MMS spacecraft in 19 quite (the X-component of the ion bulk velocity | v_i,x | < 200 km/s) and 23 active (peak value of | v_i,x | in each interval reaches at least 500 km/s) intervals. All observations were made in the midnight sector of the magnetotail ( | Y_GSE |~\,\, ~\,\,13~R_E ) and within the Sun–Earth direction range X ≈ ~\,\, - (15~-28)~R_E . It is shown that intense current structures with current density | j | > 30 nA/m2 are observed only within the BBFs and are absent in the PS during quite intervals. The probability density distributions of | E 1pt ' | , | E_||' | and j · E 1pt ' , j_|| · E_||' demonstrate similar behavior. Thus, during the quiet intervals, the typical values of | E' | , | E_||' | , and the parameters j · E 1pt ' and j_|| · E_||' do not exceed a few mV/m and tens of pW/m3, respectively. On the other hand, during the active intervals, | E 1pt ' | and | E_||' | can exceed 10 mV/m, and the parameters | j · E 1pt ' | and | j_|| · E_||' | can exceed 100 pW/m3.