# New Scenario of plasma evolution in IC 443

## TL;DR

This paper introduces a new model explaining the transition from ionizing to recombining plasma in supernova remnants, supported by spectral analysis of IC 443, revealing distinct plasma evolution pathways and cosmic ray ionization effects.

## Contribution

It proposes a novel two-recombining plasma model for SNR evolution, explaining the origin of different plasma states and associated spectral features.

## Key findings

- Successful spectral fitting with two RP components and a power law.
- Distinct ionization temperature evolution in the two RPs.
- Evidence for cosmic ray ionization influencing plasma states.

## Abstract

Most of young and middle-aged supernova remnants (SNRs) exhibit an ionizing plasma (IP), an ionizing process following a shock heated SNR gas. On the other hand, significant fractions of SNRs exhibit a recombining plasma (RP). The origin and the mechanisms of the RP, however, are not yet well understood. This paper proposes a new model that the RP is followed after the IP process taken at the first epoch of the SNR evolution. Using the high quality and wide band (0.6-10 keV) spectrum of IC 443, we nicely fitted with a model of two RP (two-RP model) plus a power law (PL) with an Fe I Kalpha line component. The ionization temperature in one RP monotonously increases from Ne-Ca, while that in the other RP shows a drastic increase from Cr-Ni. Origin and mechanism of the two-RP and PL with an Fe I Kalpha line components are possibly due to a different evolution of two plasmas and ionization by the low-energy cosmic ray.