HOPE

Overview

HOPE (Hot Onset Precursor Event) work studies the elevated soft X-ray emission that appears before the impulsive phase of many solar flares, and develops nowcasting methods that use those signatures for earlier flare alerts. Analysis draws on Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) spectra and GOES X-Ray Sensor (GOES-XRS) irradiance records.

Primary papers:

• Telikicherla, Woods & Schwab, The Astrophysical Journal, 993, 95 (2025); DOI 10.3847/1538-4357/ae0705; arXiv:2509.05234
• Telikicherla, Woods & Schwab, The Astrophysical Journal, 966, 198 (2024); DOI 10.3847/1538-4357/ad37f6
• Telikicherla et al., Solar Physics, 301, 110 (2026); DOI 10.1007/s11207-026-02705-2

Motivation

Operational flare alerts based on GOES-XRS flux thresholds are typically issued only once a flare is already in its impulsive phase. HOPE research aims to characterize pre-impulsive plasma evolution and to evaluate whether HOPE signatures can provide earlier warnings useful for high-frequency communications operators and targeted flare observing campaigns.

Methods

As reported in the peer-reviewed papers:

• Spectral fitting of DAXSS soft X-ray observations with Astrophysical Plasma Emission Code (APEC) models to derive plasma temperature, emission measure (EM), and low-FIP elemental abundance factors during flare onset.
• Isothermal temperature and EM estimates from GOES-XRS channel ratios.
• Statistical analysis of HOPE phases across DAXSS and GOES flare samples, including AIA 193 Å context for onset loop morphology (“one-loop” and “two-loop” onsets in the 2024 ApJ study).
• A HOPE-based nowcasting algorithm on GOES-XRS (2025 ApJ), later extended with a multilayer perceptron model trained to estimate flare peak magnitude and peak time for high-impact (>M5.0) flares (2026 Solar Physics).

Results / Objectives

Published findings include elevated temperatures (about 10–15 MK) and order-of-magnitude EM increases during HOPE before the impulsive phase; elemental abundance factors that evolve from coronal toward photospheric values as flares progress; and HOPE-based nowcasting that, in the reported GOES tests, produced flare alerts minutes ahead of peak (and, in the ML study’s one-week proof-of-concept, detected all four >M5.0 flares with an average lead time of 17.9 minutes relative to the NOAA R3 radio-blackout alert). Ongoing work continues to refine HOPE detection and nowcasting for space-weather applications.

Publications

• Telikicherla et al., “Advancing Solar Flare Nowcasting with Machine Learning Based Detection of Hot Onset Precursor Events,” Solar Physics 301, 110 (2026). DOI
• Telikicherla, Woods & Schwab, “Improving Solar Flare Nowcasting with the Hot Onset Precursor Event Technique,” ApJ 993, 95 (2025). DOI · arXiv
• Telikicherla, Woods & Schwab, “Investigating the Soft X-Ray Spectra of Solar Flare Onsets,” ApJ 966, 198 (2024). DOI

Collaborators

See collaborator list in the page frontmatter (core HOPE ApJ coauthors). Related ML nowcasting coauthors appear on the 2026 Solar Physics paper.