Time-Dependent Density Diagnostics of Solar Flare Plasmas Using SDO/EVE

TL;DR

This paper presents time-resolved electron density measurements of solar flare plasmas using SDO/EVE data, revealing high-temperature density evolution at 10-second cadence and its correlation with emission measure peaks.

Contribution

First to measure high-temperature electron density evolution during flares at 10-second resolution using EVE spectral data.

Findings

Peak densities of 10^11.2-10^12.1 cm^-3 during X-class flares

Density peaks correlate with emission measure peaks

Temporal density profiles reveal high-temperature plasma dynamics

Abstract

Temporally-resolved electron density measurements of solar flare plasmas are presented using data from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO). The EVE spectral range contains emission lines formed between 10^4-10^7 K, including transitions from highly ionized iron (>10 MK). Using three density-sensitive Fe XXI ratios, peak electron densities of 10^(11.2)-10^(12.1) cm^(-3) were found during four X-class flares. While previous measurements of densities at such high temperatures were made at only one point during a flaring event, EVE now allows the temporal evolution of these high-temperature densities to be determined at 10 s cadence. A comparison with GOES data revealed that the peak of the density time profiles for each line ratio correlated well with that of the emission measure time profile for each of the events studied.