How to switch defined appenders in logback - logback

Question

I have a defined logback in my project, and here is the configuration:
<?xml version="1.0" encoding="UTF-8"?>
<appender name="DAILY" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>/logApp/application.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>/logApp/application.log.%d{yyyy-MM-dd}.%i.gz</fileNamePattern>
</rollingPolicy>
<encoder>
<charset>UTF-8</charset>
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36}:%line - %msg%n</pattern>
</encoder>
</appender>
<appender name="HOURLY" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>/logApp/application.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>/logApp/application.log.%d{yyyy-MM-dd-HH}.%i.gz</fileNamePattern>
</rollingPolicy>
<encoder>
<charset>UTF-8</charset>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36}:%line - %msg%n</pattern>
</encoder>
</appender>
<root level="info">
<appender-ref ref="DAILY" />
</root>
A you can see I only use daily appender in my root configuration. How can I switch between those defined appenders (HOURLY / DAILY) in runtime?
I have tried with the following code, but my newAppender is always null:
String loggingAppender = "HOURLY";
LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
ch.qos.logback.classic.Logger root = lc.getLogger(Logger.ROOT_LOGGER_NAME);
root.detachAndStopAllAppenders();
Appender<ILoggingEvent> newAppender = root.getAppender(loggingAppender);
root.addAppender(newAppender);