How can solar X-rays affect shortwave radio communication on Earth?

Solar X-rays affect shortwave radio communication on Earth by altering the ionosphere, the atmospheric region responsible for reflecting radio waves. These effects vary based on the wavelength and intensity of the X-ray emission:12

• Soft X-rays: Long-wavelength X-rays from the solar corona help create the ionospheric layers that make shortwave communication possible. However, when solar activity increases, these emissions can raise ionospheric density to a point where radio waves are absorbed rather than reflected, thereby hampering communications.1
• Hard X-rays: Shorter-wavelength X-ray pulses, typically associated with solar flares, ionize the lowest region of the ionosphere, known as the D region. This increased ionization in the D layer causes radio waves to be absorbed instead of reflected, resulting in radio fade-outs.1

In summary, while solar radiation is essential for creating the reflective layers needed for long-distance radio transmission, excessive X-ray activity can disrupt these signals by increasing atmospheric absorption.12