  Lightning induced radio emission has been observed on solar system planets.
Lecavelier des Etangs et al. [2013] carried out radio transit observations of
the exoplanet HAT-P-11b, and suggested a tentative detection of a radio signal.
Here, we explore the possibility of the radio emission having been produced by
lightning activity on the exoplanet, following and expanding the work of
Hodos\'an et al. [2016a]. After a summary of our previous work [Hodos\'an et
al. 2016a], we extend it with a parameter study. The lightning activity of the
hypothetical storm is largely dependent on the radio spectral roll-off, $n$,
and the flash duration, $\tau_\mathrm{fl}$. The best-case scenario would
require a flash density of the same order of magnitude as can be found during
volcanic eruptions on Earth. On average, $3.8 \times 10^6$ times larger flash
densities than the Earth-storms with the largest lightning activity is needed
to produce the observed signal from HAT-P-11b. Combined with the results of
Hodos\'an et al. [2016a] regarding the chemical effects of planet-wide
thunderstorms, we conclude that future radio and infrared observations may lead
to lightning detection on planets outside the solar system.
