ACE Real-Time Shock Solutions

GOOD SHOCKS

ALL SHOCKS

Shock Analysis

The 'Good' and 'All' shock listings contain real-time shock candidates observed by SWEPAM, and combined with MAG data is analyzed by the Rankine-Hugoniot relations. The time of a shock candidate has 1 minute precision. Whether the shock is (F)orward or (R)everse is listed.

The shock solutions listed here begin August 4 2008.

The given shock analysis results are obtained by least-squares fitting of the incomplete Rankine-Hugoniot relations (temperature information not used). The following parameters from the asymptotic upstream and downstream states are presented: shock normal, n, in XYZ, the shock speed, V, given in the spacecraft frame (vs) and in the upstream plasma frame (vp), in km/s, the downstream over upstream density ratio, r_n, the downstream over upstream magnetic field strength ratio, r_b, the angle between upstream magnetic field vector and the shock normal, Th_Bn, in degrees, and the upstream Mach number, MA.

The purpose of the automated shock finding system is to find shock candidates based on bulk speed, proton density, and temperature jumps, to obtain the solutions, and reject as many false positive events as possible while keeping most of the true shocks. Shock Analysis goes further in detail on how shock candidates are rejected and what parameters describe a good shock.

The automated shock analysis not only provides a solution, but it also provides a numerical diagnostic to check whether the shock candidate is an actual shock. A 100 point system was designed (1) to award goodness of fit based on solution parameters' uncertainties, and (2) to tell whether a shock candidate is likely a strong shock. Solutions with points above ~ 50 generally constitute good solutions of true shocks. Note that weak shocks with good solutions can still result in low point values. However, weak shocks are not as important in space weather applications. A top score of 100 means the solution has low uncertainties and the candidate is a strong shock.

Note: Velocity data from SWEPAM is not provided in real-time fashion. Only bulk speed is provided in the real-time data. For the purpose of this analysis, an assumption was made that the x-component of the velocity is equal to the bulk speed.

Shocks accepted as true shocks are chosen in an automated fashion and are recorded as GOOD shocks. To view the solutions for all the shock candidates (not just the good shocks), follow the the ALL Shocks link.

References