# Application of the electromotive force as a shock front indicator in the inner heliosphere

## TL;DR

This study demonstrates that electromotive force (EMF) can effectively indicate CME shock fronts in the inner heliosphere, using automated detection algorithms and spacecraft data, revealing peaks shortly after shocks and distance-dependent properties.

## Contribution

The paper introduces an automated EMF-based shock front detection method and validates its effectiveness against existing CME data, highlighting EMF's potential as a reliable shock indicator.

## Key findings

- EMF peaks occur 0-50 minutes after shock arrival
- The detection algorithm matches most known CME events
- EMF properties follow a power law with heliocentric distance

## Abstract

The electromotive force (EMF) describes how the evolution and generation of a large-scale magnetic field is influenced by small-scale turbulence. Recent studies of in-situ measurements have shown a significant peak in the EMF while a coronal mass ejection (CME) shock front passes by the spacecraft. The goal of this study is to use the EMF as an indicator for the arrival of CME shock fronts. With Helios spacecraft measurements we carry out a statistical study on the EMF during CMEs in the inner heliosphere. We develop an automated shock front detection algorithm using the EMF as the main detection criterion and compare the results to an existing CME database. The properties of the EMF during the recorded events are discussed as a function of the heliocentric distance. Our algorithm reproduces most of the the events from Kilpua et al. (2015) and finds many additional CME-like events which proves the EMF as a good shock front indicator. The largest peaks in the EMF are found from 0 to 50 minutes after the initial shock. We find a power law of -1.54 and -2.18 for two different formulations of the EMF with the heliocentric distance.