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IF YOUR mobile phone gets cut off, don’t automatically blame the phone company. A more distant influence could be reaching down to interrupt your conversation.

It turns out that radio bursts from the Sun can disrupt mobile telephone services, especially near sunrise and sunset. The bursts come from the explosions in the Sun’s atmosphere known as solar flares, which generate powerful pulses of electromagnetic radiation lasting up to tens of minutes.

It’s the receiving antennas on cellphone base stations that are the weak point in the phone network. The antennas are aimed horizontally, to pick up signals from phones in the area. These signals can be quite faint because modern cellphones minimise radio emissions, both to extend battery life and to avoid exposing users to stronger microwaves that necessary. For most of the day the Sun is out of the antennas’ field of view, but for about half an hour at dawn and dusk the antennas are ideally placed pick up its radio emission.

To see if this might cause problems, Dale Gary from the New Jersey Institute of Technology in Newark and researchers from Bell Laboratories analysed 40 years of data on solar radio bursts powerful enough to overwhelm the faintest incoming radio signals. Call-blocking bursts happened as often as once every 3.5 days at the high points of the Sun’s approximately 10-year cycle. This fell to once in 18.5 days at the cycle’s low points. The researchers calculated that when solar activity is at a peak, an average base station would be temporarily knocked out several times a year.

The solar bursts will limit European plans to reduce the power output from cellphones, Gary told New ÐÓ°ÉÔ­´´. Even small reductions in power could make the systems far more vulnerable to the effect.