Introduction

This is a beginner's guide to RHESSI spectroscopy. It assumes that you have already set up your computer to run IDL (Version 5.3.1 or later, preferably the latest version) with the Solar Software (SSW) tree and with access to the RHESSI flight data (see Software Installation Instructions and Accessing HESSI Data). It will take you through demonstrations of the RHESSI Graphical User Interface (GUI) to the RHESSI software and the SPectral EXecutive (SPEX) package. A detailed SPEX Help document called Analyzing Flare X-ray Spectra Using SPEX is available in SSW. It includes comments on an interactive session at the command line, and a description of the available user commands and parameters. A follow-on to this First Steps document called RHESSI Spectroscopy - Second Steps has been written by Linhui Sui and Astrid Veronig and provides instructions for the more advanced capabilities of SPEX. Another guide to RHESSI spectroscopy using the IDL command-line interface has been written by Chris Johns-Krull.

The objective of this document is to demonstrate how to obtain spectra of the total solar photon flux incident on the RHESSI instrument for different time intervals during a flare. Imaging spectroscopy is not covered in this demonstration; further analysis is required to obtain spectra for different areas within an image.

The GUI is a user-friendly way to obtain light curves, images, and count-rate spectra. Currently, it can also use the instrument response function to produce so-called "semi-calibrated" photon flux spectra but without subtracting background.

SPEX takes as its input the count-rate spectra produced by the GUI (or by this IDL command-line input). (See Chris Johns-Krull's Overview of the Command Line Interface for HESSI Data Analysis Software.) SPEX defines the time intervals for analysis, determines and subtracts the background, decides on the functional form to assume for the photon spectrum, and uses the instrument response function to produce photon flux spectra. The user must provide guidance to SPEX at each step in the process as will be evident in this demonstration.

This page last updated: June 27, 2011